The automatic protection switching (Automatic Protection Switching, APS) G.8031 of Ethernet (Ethernet, ETH) defines 1+1/1:1, unidirectional/bidirectional, revertive/non-revertive switching modes, and sets forth various application scenarios and handling processes. As defined in G.8031, if the current protection group is under a 1+1 bidirectional revertive switching mode or 1:1 bidirectional revertive protection switching mode, a Signal Fail (Signal Fail, SF) alarm will trigger protection switching when a working channel fails, and the service will be switched from the working channel to a protection channel. When the working channel recovers later, the SF alarm disappears. To prevent switchback caused by the fault and jitters of the working channel, automatic protection switching (Automatic Protection Switching, APS) gets into a wait-to-restore (Wait to Restore, WTR) state first. The duration of the WTR depends on a WTR timer threshold (generally defined by a network maintainer). In the WTR time, if the working channel raises no SF alarm any more, the APS will jumps from the WTR state to a No Request (No Request, NR) (r/b=null) state. At this time, the service switches back to the working channel.
In the prior art, according to the G.8031/G.8131 protocol, in the switching process of the 1+1/1:1 bidirectional revertive mode, if two sides do not recover from the fault simultaneously, the first recovered side responds to the SF (r/b=normal) state of the second recovered side and gets into an NR (r/b=normal) state; upon receiving the information indicating that the first recovered side gets into the NR(r/b=normal) state, the second recovered side gets into a WTR state, and, upon expiry of a WTR timer, gets into the NR (r/b=null) state; at this time, the first recovered side responds to the NR (r/b=null) of the second recovered side, and also gets into the NR (r/b=null) state, and both sides switch back to the working channel. That is, when both sides do not recover simultaneously, the second recovered side gets into the WTR state, and, upon expiry of the WTR time, both sides switch back to the working channel simultaneously.
According to the technical solution in the prior art, the following problems are found in the prior art:
In the technical solution of the prior art, the first recovered side does not get into the WTR state, and therefore, the user is unable to know the WTR state of the first recovered side before the service is switched back to the working channel; and, if the WTR time set on the first recovered side is greater than the WTR time set on the second recovered side, the first recovered side possibly switches back to the working channel before the WTR time expires, which does not meet the customer requirement of switching back to the working channel upon expiry of the WTR time after the working channel is recovered.